Right size for images? (cross-post)

[StrawberryGirl]

Sorry, I originally posted this question in the wrong place by accident! Anyway, here is my question:

I had a deluxe size book made, and when I looked through it, the large images were great, but the small images were quite grainy. I assume my photos were too high in resolution. I'm having the book remade, and want to get it right this time!

My question is, what size should I reduce the photos to, for a basic 3-4 photo per-page layout? Will the MyPublisher suggestion of 2272x1704 for a full bleed deluxe photo work for the smaller photos as well? The photos are from a Canon Rebel XT 8 megapixel camera. The images are originally 3456x2304, 72 pixels/inch.

Oen other thing that is confusing me. MyPublisher suggests 2272 x 1704 images for the deluxe books. On the forums I am reading that you should use 350 dpi, and keep the images between 1 and 7 MB. If I follow the suggested dimensions of MyPublisher, at 350 dpi, it comes out to around 10 mb. Isn't this too high?

Thanks!

[LauraG]

Strawberry Girl: I'm not helping at all. I'm in the same boat. I guess what I'm looking for is HOW do you change the dpi in PhotoShop? I can only see changing the ppi (pixels/inch). Would changing the ppi to 350 be the same as dpi or is it a completely different conversion?

[StrawberryGirl]

I think dpi and ppi are interchangable- someone correct me if I'm wrong!

[rfredley]

I'm pretty sure ppi and dpi are the same thing. Pixels per inch. Dots per inch. Don't confuse with lpi which is lines per inch and speaks to how many halftoning lines you get in an inch.

The absolutely most precise way to get the cleanest best image is to resize all your images to 350dpi/ppi at the final output size before you import them into the bookmaker software. This is a VERY time consuming and painful process.

I'm not convinced that there's a significant loss in quality by delivering them a larger image than they request. Though if you're seeing it, it's quite possible. I don't typically use smaller image templates, though I'm shooting 10megapixel raw images.

Regardless, it takes more of their resources to handle those files though, and if everyone starts uploading these huge files they may decide to downsample your images with the bookmaker software before they're uploaded resulting in double compression which nobody wants.

If you're looking for the dialog box that handles image resizing, you need to go to: Image > Image Size which will pop up the appropriate dialog box. Resize your image in pixels, change the dpi/ppi values. Save out as a jpeg.

One more things about jpeg images. You could have 2 images that were both saved with the same pixel dimensions that were dramatically different sizes in megabytes. That's due to the way jpeg compression works. To simplify, jpeg compresses gradients and flat areas and highlights edges. The more edges are in your image, the bigger your file is going to be. That's why your photos in the woods are always huge and your photos at the beach are typically pretty tiny. There are just a lot more details to keep in the woods. That may be why you have a 10mb file where your friend only has a 1-5 mb one.

Edited because I noticed that Strawberry Girl actually had pixelated images that were reduced.


Message was edited by: rfredley

[DonC]

Actually dots per inch (dpi) and pixels per inch (ppi) are not the same at all. PPI is an imput measure. Dots per inch is a measure of how many dots a the printer can lay down in an inch.

Unless you have a continuous tone device, which we don't here, ppi and dpi will not be the same and are not directly related. For inkjets the ppi would normally be between 150 and 250, depending on the image. I've seen at least one person assume we have a press and that suggest that the ppi should be set to twice the lpi, or lines per inch.

That's fine in that the rule of thumb is stated correctly, but I wonder given the lpi number, which he put at 175. Seems high. Since lpi is essentially dpi divided by the number of halftones in a spot, and since you want at least 256 shades (16 X 16), an lpi of 175 suggests a dpi of 2800. That's very impressive. Perhaps too impressive.

The bottom line is that unless you know the technology the printer is using it's hard to say what the ppi should be. In any event I've just uploaded at whatever size I've had and it's worked fine. I'm sure some had to be upsampled and some downrezzed quite a bit but the driver seems to have handled this without a problem.

> I'm pretty sure ppi and dpi are the same thing.
> Pixels per inch. Dots per inch. Don't confuse with
> lpi which is lines per inch and speaks to how many
> halftoning lines you get in an inch.
>
> The absolutely most precise way to get the cleanest
> best image is to resize all your images to 350dpi/ppi
> at the final output size before you import them into
> the bookmaker software. This is a VERY time
> consuming and painful process.

[rfredley]

Wow, you know that makes too much sense. :)

However, I'd be willing to be that 9/10 most people around here (incorrectly) use the terms interchangeably to describe the output print metadata flags in your original photoshop file with a target resolution of pixels in an inch.

Kinda the way we tend to call typefaces fonts when fonts are really just files that allow computers to render text in different typefaces. :)

Or maybe not at all.

Regardless, thanks for the clarification.


> Actually dots per inch (dpi) and pixels per inch
> (ppi) are not the same at all. PPI is an imput
> measure. Dots per inch is a measure of how many dots
> a the printer can lay down in an inch.
>

[irusan]

Actually, a font is a 'specific type family, in a specific face, at a specific size'. Think of Times New Roman Regular 12 point: Times New Roman would be the family, Regular would be the face and 12 points would be the size. So, Times New Roman Regular 12 point is indeed a "font". It's a completely different font than Times New Roman Italic 12 point or Times New Roman Regular 10 point.

But you're right about people using the terms interchangeably.

I'm also the one that keeps mentioning to double the LPI for your prints. The LPI value of 175 was given to me by MyPublisher and, a while ago, re-confirmed when there was some question about whether the LPI was 175 or 180.

Perhaps it's time for me to "come out of the closet" and give y'all my background. While I am a professional photographer, I am not a full-time photographer. Too many bills to pay for that :)

I work full time for a company that produces variable data software for the print industry. I work with RIPs and virtually every manufacturer of presses on a daily basis (both digital and off-set). Given the amount of "advice" I've given on these forums, I figured that, in the interest of full disclosure, I should mention my background.

I certainly agree that the resolution of 175 LPI is, as DonC correctly points out, very impressive, however I've been to print shops that use as high as 240 LPI for fine art photography catalogs. So it's not unheard of to have LPI values as high as 170 or 180 for printing photographs. I know some people disagree and that's cool - I'll still use 350 DPI (not PPI) for setting my images in MyPublisher.

Don, it sounds like you work for MyPublisher? If so, then are you saying that you folks don't have the press and broker it out?

Thanks

Rob